Electrode carrier means for well



`Fam. 24, 1956 A. BLANCHARD ETAL `ELECTRODE CARRIER MEANS FOR WELL LOGGING APPARATUS Filed June 27, 1952 INVENTORS. ANDRE BLANCHARD Agip ICE MENNECIER.DCD. NECIER, EXE UTRI (221 THEIRATTORNEYS.

MAUR Y ALlNE MEN SM l0.

3s FiGB United States Patent ELECTRODE CARRIER MEANS FOR WELL LGGING APPARATUS Andre Blanchard, Houston, Tex., and Maurice Mennecier, deceased, late of Houston, Tex., by Aline Mennecier, executrix, Houston, Tex., assiguors to Schlumberger Well Surveying Corporation, Houston, Tex., a corporation of Delaware Application June 27, 1952, Serial No. 295,996

Claims. (Cl. 324-10) The present invention relates to electrical well logging apparatus and -more particularly to new and improved electrode carrier means which is adapted to maintain the bore hole electrodes either in physical contact with or in close proximity to the side wall of the bore hole regardless of the roughness thereof, while providing eiective insulation of the electrodes both from each other and from any conducting liquid that may be present in a well.

In several electrical logging techniques currently in use, it is essential that the bore hole electrodes be maintained either in physical contact with or in close proximity to the side wall of the bore hole and electrically insulated both from each other and from any conducting liquid contained in the bore hole. It has been proposed to meet these requirements by mounting the electrodes in a ilexible insulating cushion member or pad provided with suitable means for urging the pad into engagement with the bore hole. ln bore holes having relatively smooth side walls, this construction has been elective in maintaining good electrical contact between the electrodes and the well wall as the logging apparatus is raised through the bore hole.

However, where the wall surfaces of the bore hole are highly uneven because of sloughing or enlargements in the vicinity of friable formations or particularly from grooves made in the well wall by the drill bit, it is not always possible for the cushion member to keep the electrodes in proper relation to the wall of the well. Moreover, the differences in curvature encountered in bore holes of greatly different diameters cannot always be ac coinmodated by a single well logging apparatus to the extent necessary to meet fully the requirements stated above. As a result, it has been the practice to provide cushion members of dierent sizes and to use the one having the proper curvature for the diameter of the particular well to be logged.

It is an object of the invention, accordingly, to provide new and improved electrode carrier means for well logging apparatus which is free from the above-noted deficiencies of the prior art.

Another object of the invention is to provide new and improved electrodecarrier means of the above character which is capable of maintaining the bore hole electrodes in well logging apparatus or the like in physical contact with or in close proximity to the side wall of the bore hole regardless of the degree of roughness or unevenness of the side wall.

A further object of the invention is to provide new and improved electrode carrier means of the above character embodying means for maintaining the bore hole electrodes effectively insulated from one another and from any conducting liquid contained in the bore hole despite any unevenness in the side wall of the bore hole.

Still another object of the invention is to provide new and improved electrode carrier means of the above character which is readily conformable to side wall curvatures of different radii whereby it may be employed effectively in bore holes of different diameter.

According to the invention, electrode Gamer means is firice provided which comprises a hollow cushion member made of highly flexible, relatively inelastic material and partially iilled with a nonconductive iluid which serves to prevent complete collapse of the cushion member while permitting it to assume a variety of desired shapes. The cushion member may be mounted on a support adapted to be lowered into a well and having means for urging the cushion member into engagement with the side wall of the hole. The logging electrodes may be mounted on or in the face of the cushion member which lies opposite the well wall.

With this construction, it will be apparent that the outer face of the cushion member will readily conform to any unevenness in the well wall that may be encountered, so that the electrodes will be maintaine'd in proper relation to the well wall and effectively insulated from each other and from any conducting liquid that may be present in the bore hole. By the same token, it will readily conform to a relatively wide range of side wall curvatures so that it may be employed effectively in bore holes of different diameters.

For a better understanding of the invention reference is made to the accompanying drawings of a typical embodiment in which: l

Fig. 1 is a side view of electrode carrier means constructed according to the invention in position in a Well;

Fig. 2 is an enlarged view in longitudinal section of the cushion member employed in the electrode carrier means of Fig. l;

Fig. 3 is a view in transverse section taken along line 3--3 of Fig. 2 and looking in the direction of the arrows; and

Fig. 4 is a view similar to Fig. 3 showing the cushion member in a bore hole of smaller diameter.

By way of example, the invention will be illustrated herein in a forni suitable for use in wells containing a column of conducting liquid, although it will be understood that the invention may be used with equal effectiveness in dry holes. Referring to Fig. l, a well logging as sembly 10 is shown disposed in a bore hole 11 containing a column of relatively conducting liquid 12. The logging assembly may comprise, for example, a tubular support 13 adapted to be lowered and raised in the bore hole 11 on a supporting cable 13a by suitable means (not shown) located at the surface of the earth.

Mounted on the tubular support 13 is a spring cage assembly .which may comprise, for example, a plurality of bowed springs 14 and 15, the opposite ends of which may be rigidly secured to a pair of collars 16 and 17,

respectively, slidably mounted on the tubular member 13. The bowed spring 14 carries a wall engaging cushion member 18 constructed according to the invention and the bowed spring 15 may support a cushion member 19, as shown. With this construction, the forces on the assembly 10 are balanced symmetrically so that the tubular member 12 is maintained substantially centered in the bore hole 11. Also, the bowed springs 14 and 15 are preferably designed so as to exert substantially constant pressure between the cushion member 18 and the side wall of the bore hole regardless of the diameter of the bore hole 11.

Considering now Fig. 2, the cushion member 18 may have a rear wall 19 molded on the bowed spring 14 at a location intermediate the ends thereof and a front wall 20 enclosing a volume 21 of given size. The front wall 20 is preferably thinner than the rear wall 19 and both walls may be made from a suitable, highly flexible, nonelastic material having good wearing properties such as neoprene, for example. Welded or otherwise suitably secured to the bowed spring 14 is a backing member 22 which serves to impart rigidity to the rear wall 19.

Formed in the front wall 20 of the cushion member 18 are a plurality of recesses 23, 24 and 25 within which may be molded or otherwise secured a plurality of metal electrodes 26, 27 and 28. Preferably,. the. electrodes 26, 21 and 2s are sunk in the recesses 23, 24 andzs, respectively, so that theyare maintained in close proximity to but out of physical contact with the side wall of the bore hole, as shown in Fig. 2. With this construction, undesirable potentials which might be created if the electrodes were torub against the side wall of the bore hole are elimin'ated yet good electrical contact with the formations is maintained through the conductive drilling mud which lls the recesses 23, 24 and 25.

The electrodes 26, 27 and 28, respectively, are connected to the insulated conductors 29, 3i) and 31, respectively, which pass through watertight bores 32, 33 and 34 formed in the rear wall 19, the bowed spring 14 and the backing member 22. The conductors 29, 30 and 31 pass into the tubular member 13 and up to the surface of the earth through the supporting cable 13a (Fig. 1). Sulicient slack should be maintained in the portions of the conductors 29, 30 and 31 which lie within the volume 21 so as to prevent undue stressing of these conductor portions as the front face 20 of the cushion member 18 moves away from the rear face 19 in accommodating itself to any unevenness in the wall of the bore hole 11.

The volume 21 lying between the front wall 20 and the rear wall 19 of the cushion member 18 is partially lled with a nonconducting fluid 35, such as oil, for example, which may be introduced through a small tubular passage 36 extending through the rear wall 19, the backi ing member 22 and the bowed spring 14. The air re maining in the portion of the volume 21 not occupied by the fluid 35 is withdrawn and the tubular passage 36 is closed by a suitable closure member 37. Under these conditions, the front face 20 of the cushion member 18 contracts to accommodate snugly the volume of fluid 35 contained in the cushion member 18, and when the apparatus is out of the well so that the cushion member 18 is not restrained in any way, the front face 20 will bulge out slightly at its lower end with respect to the rear wall 19 due to the weight of the Huid 35.

When the apparatus 10 is lowered into a well and the cushion member 18 is urged into engagement with thc side wall thereof by reason of the bowed springs 14 and 15, the front wall will be moved closer to the rear wall 19 and the fluid 35 thus displaced will move to upper, lower and side portions of the volume 21 not theretofore occupied by the fluid.

Because of the fact that the fluid pressure behind the front face 20 of the cushion member 18 acts equally in all directions, the front face 20 will assume the shape or outline of the side wall of the bore hole l1, as shown in Fig. 2. As a result, the electrical contacts between the electrodes 26, 27 and 28 and the side wall of the bore hole will all be equally effective. mud or mud lm lying between the front face 20 of the cushion member 18 and the side wall of the bore hole 11 which might otherwise shunt the electrodes 26, 27 and 28 will be squeezed out therefrom.

By virtueof the extremely flexible character of the front face 20 of the cushion member 18 and the fact that the pressure of the nouconductive Huid in the volume 21 acts equally in all directions, the electrodes 26, 27 and 28 will be maintained in good electrical contact with the side wall of the bore hole 11 even for pronounced enlargements having vertical dimensions less than those of the cushion member 18. These same prope erties enable the cushion member 18 to adapt itself readily to the different curvatures encountered in bore holes of different diameter, as shown in Fig. 4, in which it is disposed in a bore hole of lesser diameter than in Fig. 3.

If the apparatus is to be used in a dry bore hole, it Will be understood that the electrodes 26, 27 and 28 would not be recessed, as shown in Fig. 2, but will be mounted Moreover, any

4 directly on the surface of the front face 20 so as to be in direct electrical contact with the side wall of the bore hole 11. Alternatively, the electrodes 26, 27 and 28 may be electro-deposited on the surface of the cushion member 28.

In a typical apparatus designed for use in well logging operations, the cushion member may be approximately 5 inches wide and l5 inches long and the front wall 20 may be approximately 3716 of an inch thick, or less. Approximately of the total volume 21 inside the cushion member 18 may be lled with uid, although this value is not critical, the air occupying the remaining portion of the total volume being withdrawn so that the cushion member surfaces snugly bound the fluid, as described above.

Theinvention thus provides novel and highly effective electrode carrier means for Well logging7 apparatus and the like. By utilizing a partially collapsed cushion member enclosing a volume filled with nonconducting fluid and having a front well wall engaging wall made of thin, highly flexible, relatively inelastic material, electrodes mounted in or on the front wall may be maintained either in physical contact with or in close proximity to the side wall of the bore hole, regardless of the roughness thereof, 'and the electrodes may be kept insulated both from each other and from any conducting duid that may be present in the well.

It will be understood that the specific embodiment described above and shown in the drawings is susceptible of considerable modification within the spirit of the invention. For example, while bowed springs have been shown for urging the cushion member against the side wall of the bore hole, any suitable expanding means for accomplishing this purpose may be utilized. Also, any relatively inelastic, highly ilexible material having good wearing properties may be employed for the cushion member 18. The speciic embodiment shown, therefore, is to be regarded only as exemplary and not as restricting the scope of the following claims.

We claim:

1. Bore hole apparatus comprising an elongated support adapted to be moved through a bore hole, a plurality of bowed spring members secured at opposite ends to members mounted for limited sliding movement on said support, said bowed spring members having intermediate portions normally urged outwardly towards the wall of the bore hole, a hollow closed cushion member enclosing a nonconducting liquid and having a front Wall and a rear wall of exible insulating material, said rear wall of said cushion member being mounted on said intermediate portion of one of said bowed spring members, at least one electrode carried by said front wall of said cushion member and adapted to be in electrical communication with the wall of the bore hole, and conductor means connected to said electrode and passing through said cushion member from said front wall to said rear wall, the portion of said conductor means passing through said cushion member having suicient slack to accommodate relative movement between said front wall and said rear wall.

2. Bore hole apparatus as described in claim l wherein said electrode is mounted on the outer face of said front wall of said cushion member.

3. Bore hole apparatus as described in claim l wherein said electrode is disposed in a recess formed in the front wall of said cushion member.

4. Bore hole apparatus comprising an elongated support adapted to be moved through a bore hole, a plurality of bowed spring'members secured at opposite ends to members mounted for limited sliding movement on said support, said bowed spring members having intermediate portions normally urged outwardly toward the wall of the bore hole, a hollow closed cushion member enclosing a non-conducting liquid and having a front Wall and a rear wall of exible insulating material, said rear wall having embedded therein a rigid backing plate and at least part of said intermediate portion of one of said spring members, said backing plate being attached to., said spring member, at least'one recess in the outer face of said front wall,'an electrode mounted in said recess and adapted to be in electrical communication with the wall of the bore hole, and conductor means connected to said electrode an d passing through said cushion member from said front wall to said rear wall, the portion of said conductor means passing through said cushion member having sufficient slack to accommodate relative movement between said front wall and said rear wall.

5. Bore hole apparatus comprising an elongated support adapted to be moved through a bore hole, a hollow closed cushion member enclosing a nonconducting liquid and having a front wall and a rear wall of exible insulating material, means mounting said cushion member on said support and urging said cushion member outwardly towards the wall of the bore hole, at least one electrode carried by said front'wall of said cushion member and adapted to be in .electrical communication with the wall of the bore hole, and conductor means connected to said electrode and passing through said cushion member from said front wall to said rear wall, the portion of said conductor.means passing through said cushion member having suicient slack to accommodate relative movement between said front wall and said rear wall.

References Cited in the le of this patent UNITED STATES PATENTS Re. 23,621 Hilderbrandt Feb. 24, 1953 2,233,420 Leonardon Mar. 4, 1941 2,427,950 Doll Sept. 23, 1947 FOREIGN PATENTS 643,531 Great Britain Sept. 20, 1950 

